Forty aerobic and 20 anaerobic bacterial isolates obtained from monkey plaque have been screened to determine whether they produce an IgAl protease specific for monkey IgA. While a number appear to possess proteases capable of hydrolyzing monkey IgA none, so far, appear capable of cleaving monkey IgA at the hinge region to produce Fab and Fc fragments. Attempts to identify particular isolates have proved difficult as the monkey isolates seem not to fall readily into existing taxonomic schemes. Monomeric IgA has been purified from a pool of normal monkey serum. Attempts to determine the distribution of the 1 and 2 subclasses in the purified monkey serum using monoclonal and monospecific antibodies to human IgAl and 2 has not been successful because these reagents do not appear to cross-react with monkey IgA. IgAl protease from Streptococcus sanguis l0556 has been partially purified by high performance liquid chromatography. Pregnant monkeys have been immunized with type l fimbriae of A. viscosus and type 2 fimbriae of A. naeslundii and A. viscosus in an attempt to produce colostral IgA and serum IgG antibodies.